Befaco Even VCO

Name: Befaco VCO
Brand: Befaco

At 8 HP, it fits into tight Eurorack systems.

Overview

The Befaco Even VCO is a voltage-controlled oscillator module for Eurorack synthesizers. It was built for stability and tracking accuracy. Owners report a classic analog oscillator sound with clean tuning across up to 10 octaves, from sub-bass fundamentals to ultrasonic textures. It's not flashy, but the engineering is serious. It's designed for ultra-precise tracking even when the power fluctuates, which matters in modular setups where voltage rails aren't always perfectly regulated. The module has a 10-position rotary octave selector, so you change pitch range right away without hunting through fine-tune knobs.

The core waveform outputs aren't fully documented across all sources. One output, labeled "even," is confirmed to deliver a sine wave at the fundamental frequency, which suggests a focus on harmonic purity. It also offers linear FM, hard sync, and PWM. Some users have studied its source code to implement DPW (discrete time piecewise) alias suppression techniques in other designs.

The Even VCO has a reputation among builders and technicians for being finicky to calibrate. Multiple forum reports cite "impossible calibration" scenarios, and one user noted their unit was out of calibration upon arrival. Discussions on Sequencer.de point to possible voltage control accuracy problems from incorrect resistor values. Specifically, they say non-calibratable units need a 100 Ohm 3300ppm 0805 SMD tempco resistor. These are not widespread failure reports, but they form a consistent thread. The module demands care in build and setup.

Specifications

Manufacturer	Befaco
Model	Even VCO
Type	Eurorack Oscillator Module
Width	8 HP
Depth	22mm (28mm for DIY version including power connector) (Juno) / 47mm (Perfect Circuit)
Current Draw	36mA @ +12V, 26mA @ -12V
Frequency Range	Cleanly tuneable over 10 octaves
Tracking Accuracy	Up to 1 Cent per octave
Features	Linear FM, Hard Sync, PWM, 10-position octave selector
Outputs	Sine wave at fundamental frequency (“even” output)

Key Features

10-Octave Tunable Range with Rotary Octave Selector

Tuning across 10 octaves is no small feat in analog VCO design, and the Even VCO handles it with a dedicated 10-position rotary switch. Players can jump octaves instantly, which helps in live performance or sound design sessions where timbral shifts need to be immediate. The switch gives mechanical feedback and removes the guesswork of dialing in octaves with a continuous knob, reducing drift and tuning errors.

Ultra-Precise Tracking Under Voltage Fluctuations

Stability is one of the Even VCO's main design goals. It's explicitly designed to hold accurate pitch when power supply voltages fluctuate, a common issue in densely packed Eurorack cases. According to available documentation, it achieves tracking accuracy within 1 cent per octave, which is exceptional for a discrete analog oscillator. That precision makes it viable for polyphonic patches or stacked oscillators, where even slight detuning becomes audible.

Linear FM, Hard Sync, and PWM Modulation

Linear FM gives dynamic pitch sweeps and metallic timbres when driven by envelopes or LFOs. Hard sync gives aggressive, harmonically rich leads and digital-sounding sweeps. PWM (pulse width modulation) adds movement to square waves, from hollow phasing to thick chorusing. These are standard features in high-end VCOs.

Even Output as Fundamental Sine Wave

Collectibility & Value

The Befaco Even VCO has appeared on the used market in working condition, tested and sold with a ribbon power cable, though described as showing signs of use. A new unit was listed at C$430.49, while a full DIY kit was priced at £98.00 (excl. VAT) from Thonk, and a ready-built version at 198 € from Thomann.de. These prices are higher than entry-level DIY kits but below boutique hand-built modules. Calibration difficulties reported by users may affect long-term reliability and resale appeal, particularly for non-technical buyers. Units that are properly calibrated and tested hold more value, and DIY builders should expect to invest time in setup.